Monday, June 29, 2015

Tonight's Sky for June 29: Mercury at its Best

Want
to join a small club of people who have seen the planet Mercury?
Well, here's your chance as the first planet from the Sun will be
making its best appearance of the fall this morning.

Of all
the Classical Planets (those known to the Ancient Greeks and Romans),
Mercury is by far the hardest to spot because, as seen from Earth, it
never gets very far away from the Sun. As a result, Mercury is often
obscured from view by the Sun's glare.

As
of today, Mercury has reached a point in its orbit called greatest
elongation, which is a fancy way of saying that, as seen from Earth,
Mercury is as far from the Sun as it will get on this orbit and
making its best morning appearance of the year. How good is it? So
good that Mercury sets about an hour and a half after the Sun! So
good that, even 30 minutes after sunset, Mercury is still about 10
degrees up from the horizon. To simulate, hold your fist vertically
at arm's length. While that may not seem overly high, for elusive
Mercury, that's quite good.

So,
take a moment or two, go out just before dawn, and try to spot
Mercury. If you are successful in spotting the speedy planet, you are
accomplishing something that the great astronomer Nicolaus Copernicus
(who rediscovered the idea of a sun-centered solar system) supposedly
never did.